What is brucellosis? Brucellosis is an infectious disease caused by the bacteria of the genus Brucella. These bacteria are primarily passed among animals, and they cause disease in many different vertebrates. Various Brucella species affect sheep, goats, cattle, deer, elk, pigs, dogs, and several other animals. Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria. In humans brucellosis can cause a range of symptoms that are similar to the flu and may include fever, sweats, headaches, back pains, and physical weakness. Severe infections of the central nervous systems or lining of the heart may occur. Brucellosis can also cause long-lasting or chronic symptoms that include recurrent fevers, joint pain, and fatigue.

Brucellosis is not very common in the United States, where100 to 200 cases occur each year. But brucellosis can be very common in countries where animal disease control programs have not reduced the amount of disease among animals.

Brucellosis is a disease caused by a bacteria, Brucella canis. It is found throughout the world. It is spread through contact with aborted fetuses and discharges from the uterus of infected bitches, during mating, through maternal milk and possibly through airborne transmission in some cases. The bacteria enters the body through mucous membranes and spreads from there to lymph nodes and the spleen. It also spreads to the uterus, placenta and prostate gland as well as other internal organs at times.

In female dogs, infection leads to abortion or early death of infected puppies. Infected females may have no other clinical signs. In some cases there may be decreased fertility rather than abortion. This may be due to resorption of fetuses early in their development.

          The most common sign of brucellosis infection in a healthy-appearing bitch is abortion between days 45 to 59 of gestation. The vaginal discharge associated with abortion is typically brown or greenish gray in color. This vaginal discharge and fetuses contain large numbers of Brucella bacteria. Other dogs and humans should not come in contact with these secretions. When an infected bitch aborts, spread throughout a kennel can be very rapid. The persistent discharge after abortion contains extremely high numbers of organisms for 4 to 6 weeks. Milk also serves as another contaminant to the environment. Infected bitches may deliver both living and dead puppies. These surviving puppies are infected and will shed bacteria in their secretions.

Bitches infected with B. canis may appear infertile. These bitches typically do conceive a litter, but resorb the fetuses early during gestation. Brucellosis should always be considered when a dog is examined for infertility.

In male dogs, infection of the testicles can lead to infertility due to anti-sperm antibodies developed as the body attempts to fight off the bacterial infection. The testes may atrophy after the initial period of swelling. Scrotal enlargement or infection of the skin over the scrotum may be seen.

In both female and male dogs there may be infection of spinal discs (diskospondylitis) which can cause back pain and rear leg weakness or even paralysis. Eye inflammation may be seen in either sex. It is not usually possible to culture Brucella canis bacteria from the blood or affected tissues so diagnosis is usually done by titer testing. There is a kit available to veterinarians for testing in their office. It is usually best to retest any dogs found positive on this test with other testing methods since there is a fairly high rate of false positives using the in-house test kit.

The Rapid Slide Agglutination Test (RSAT) is a widely used screening test for brucellosis in dogs. A blood sample is taken from the dog to be tested, and serum is separated. Patient serum is mixed with heat-killed Brucella ovis on a microscope slide. B. ovis is used because it is similar to B. canis. Agglutination of the serum sample is suspicious for B. canis infection. This test is highly sensitive, and false-positive reactions do occur. A false positive is a test that appears positive in a dog that is not infected with the disease. These false-positive reactions are caused by cross- reactions with Bordetella bronchiseptica (the kennel cough agent), Pseudomonas, Moraxella, and other gram negative bacteria. Thus if the RSAT is negative, it is safe to assume that the dog does not have brucellosis. However, if RSAT is positive, further testing is necessary to determine if the patient is infected with Brucella canis. Typically, the 2-mercaptoethanol tube agglutination test (2- ME TAT) is used in these patients. Few false-positives result with this test. A dog that tests positive with the 2-ME TAT should have the results confirmed using an agar gel immunodiffusion test (AGID), or blood culture.

Brucellosis is very difficult to treat successfully. A combination of minocycline and streptomycin is thought to be most effective but is expensive. Tetracycline can be substituted for the minocylcine to reduce costs but also lowers the effectiveness of treatment. All infected animals should be neutered or spayed to prevent sexually related transmission. All infected animals should be considered to be lifelong carriers of the disease, even if treated.

          Dogs with brucellosis should never be used for breeding and euthanasia is the only solution to the problem. These animals are a potential source of infection for other dogs and humans. Combination therapy of aminoglycosides and tetracyclines has been tried, but the treatment only makes the infected dog test "false" negative, when in fact the dog is still very infectious and very much contagious. A breeding bitch in a kennel should be permanently separated from the other dogs to minimize the chance of spread. Euthanasia is the only true remedy for a dog that has tested positive for brucellosis using the AGID test which is the blood culture. Remember that a neutered, spayed, and/or antibiotic treated dog is still a source of infection to other dogs and humans so this is not a proper option to exercise, even though some vets are wrongly doing so.

          Unfortunately, there is no vaccine available for the prevention or treatment of brucellosis. Any new additions brought into the breeding kennel should be isolated for at least one month, and should have two negative brucellosis tests one month apart before being allowed into the kennel. Stud dogs that are actively breeding should be tested at least once every three months. Dogs and bitches competing regularly in field trials should be tested once per month and kept segregated from the main kennel area where breeding studs, brood bitches, and puppies are kept. Brucellosis-infected bitches should not be bred, even with artificial insemination, due to the risk of contamination from vaginal discharge, milk, and puppies. If a dog or bitch in the main kennel area does test positive for brucellosis, the entire kennel must be tested. Several tests should be done on each dog, each one a month apart, to make sure that all positive animals are identified, and then immediately destroyed and properly disposed of.

It would probably be best not to breed dogs without testing both the male and female for this disease. Breeding should be a deliberate choice -- not a random event! For breeding kennels, routine isolation of new dogs would be a very good idea. After isolation and negative tests at entry into the kennel and one month later, it should be safe to let the new dog mix with the others in the kennel. If infection is suspected at any time, quaternary ammomium (like Roccal Rx) and iodophor (Betadine Rx) disinfectants can kill Brucella organisms in the kennel to limit spread of the disease.

Humans are generally infected in one of three ways: eating or drinking something that is contaminated with Brucella, breathing in the organism (inhalation), or having the bacteria enter the body through skin wounds. The most common way to be infected is by eating or drinking contaminated milk products. When sheep, goats, cows, or camels are infected, their milk is contaminated with the bacteria. If the milk is not pasteurized, these bacteria can be transmitted to persons who drink the milk or eat cheeses made it. Inhalation of Brucella organisms is not a common route of infection, but it can be a significant hazard for people in certain occupations, such as those working in laboratories where the organism is cultured. Inhalation is often responsible for a significant percentage of cases in abattoir employees. Contamination of skin wounds may be a problem for persons working in slaughterhouses or meat packing plants or for veterinarians. Hunters may be infected through skin wounds or by accidentally ingesting the bacteria after cleaning deer, elk, moose, or wild pigs that they have killed.